Load a file's head text on file load just to get started

crates/project/Cargo.toml

@@ -52,6 +52,7 @@ smol = "1.2.5"
 thiserror = "1.0.29"
 toml = "0.5"
 rocksdb = "0.18"
+git2 = "0.15"
 
 [dev-dependencies]
 client = { path = "../client", features = ["test-support"] }

crates/project/src/fs.rs

@@ -1,9 +1,11 @@
 use anyhow::{anyhow, Result};
 use fsevent::EventStream;
 use futures::{future::BoxFuture, Stream, StreamExt};
+use git2::{Repository, RepositoryOpenFlags};
 use language::LineEnding;
 use smol::io::{AsyncReadExt, AsyncWriteExt};
 use std::{
+    ffi::OsStr,
     io,
     os::unix::fs::MetadataExt,
     path::{Component, Path, PathBuf},
@@ -29,6 +31,7 @@ pub trait Fs: Send + Sync {
     async fn remove_file(&self, path: &Path, options: RemoveOptions) -> Result<()>;
     async fn open_sync(&self, path: &Path) -> Result<Box<dyn io::Read>>;
     async fn load(&self, path: &Path) -> Result<String>;
+    async fn load_head_text(&self, path: &Path) -> Option<String>;
     async fn save(&self, path: &Path, text: &Rope, line_ending: LineEnding) -> Result<()>;
     async fn canonicalize(&self, path: &Path) -> Result<PathBuf>;
     async fn is_file(&self, path: &Path) -> bool;
@@ -161,6 +164,38 @@ impl Fs for RealFs {
         Ok(text)
     }
 
+    async fn load_head_text(&self, path: &Path) -> Option<String> {
+        fn logic(path: &Path) -> Result<Option<String>> {
+            let repo = Repository::open_ext(path, RepositoryOpenFlags::empty(), &[OsStr::new("")])?;
+            assert!(repo.path().ends_with(".git"));
+            let repo_root_path = match repo.path().parent() {
+                Some(root) => root,
+                None => return Ok(None),
+            };
+
+            let relative_path = path.strip_prefix(repo_root_path)?;
+            let object = repo
+                .head()?
+                .peel_to_tree()?
+                .get_path(relative_path)?
+                .to_object(&repo)?;
+
+            let content = match object.as_blob() {
+                Some(blob) => blob.content().to_owned(),
+                None => return Ok(None),
+            };
+
+            let head_text = String::from_utf8(content.to_owned())?;
+            Ok(Some(head_text))
+        }
+
+        match logic(path) {
+            Ok(value) => return value,
+            Err(err) => log::error!("Error loading head text: {:?}", err),
+        }
+        None
+    }
+
     async fn save(&self, path: &Path, text: &Rope, line_ending: LineEnding) -> Result<()> {
         let buffer_size = text.summary().len.min(10 * 1024);
         let file = smol::fs::File::create(path).await?;
@@ -748,6 +783,10 @@ impl Fs for FakeFs {
         entry.file_content(&path).cloned()
     }
 
+    async fn load_head_text(&self, _: &Path) -> Option<String> {
+        None
+    }
+
     async fn save(&self, path: &Path, text: &Rope, line_ending: LineEnding) -> Result<()> {
         self.simulate_random_delay().await;
         let path = normalize_path(path);

crates/project/src/worktree.rs

@@ -446,10 +446,10 @@ impl LocalWorktree {
     ) -> Task<Result<ModelHandle<Buffer>>> {
         let path = Arc::from(path);
         cx.spawn(move |this, mut cx| async move {
-            let (file, contents) = this
+            let (file, contents, head_text) = this
                 .update(&mut cx, |t, cx| t.as_local().unwrap().load(&path, cx))
                 .await?;
-            Ok(cx.add_model(|cx| Buffer::from_file(0, contents, Arc::new(file), cx)))
+            Ok(cx.add_model(|cx| Buffer::from_file(0, contents, head_text, Arc::new(file), cx)))
         })
     }
 
@@ -558,13 +558,19 @@ impl LocalWorktree {
         }
     }
 
-    fn load(&self, path: &Path, cx: &mut ModelContext<Worktree>) -> Task<Result<(File, String)>> {
+    fn load(
+        &self,
+        path: &Path,
+        cx: &mut ModelContext<Worktree>,
+    ) -> Task<Result<(File, String, Option<String>)>> {
         let handle = cx.handle();
         let path = Arc::from(path);
         let abs_path = self.absolutize(&path);
         let fs = self.fs.clone();
         cx.spawn(|this, mut cx| async move {
             let text = fs.load(&abs_path).await?;
+            let head_text = fs.load_head_text(&abs_path).await;
+
             // Eagerly populate the snapshot with an updated entry for the loaded file
             let entry = this
                 .update(&mut cx, |this, cx| {
@@ -573,6 +579,7 @@ impl LocalWorktree {
                         .refresh_entry(path, abs_path, None, cx)
                 })
                 .await?;
+
             Ok((
                 File {
                     entry_id: Some(entry.id),
@@ -582,6 +589,7 @@ impl LocalWorktree {
                     is_local: true,
                 },
                 text,
+                head_text,
             ))
         })
     }